Thank you for the Panorama translation!!

I'm quite puzzled with the 端程山 kanji title as well, but here are some ideas that came to mind:

1) "Mountains spanning from end to end". Like a panorama picture of a mountain range, representing MyGO's long journey, almost insurmountable (it can't fit in a single picture!!). The initial thought I got from 端程 was "spanning (程) until the end (端)", or it can be an alternative way of expressing "端から端まで" without just doubling the kanji in the title.

My initial instinct is for the panorama to be horizontal (like this https://commons.wikimedia.org/wiki/File:Uluguru_Mountain_Ranges_Panorama.jpg), but the lyrics seem to suggest a "vertical panorama" of the mountains piled up high so this might be way off base

2) "程山" in reverse is "山程 (yamahodo)" or "a lot of". Personally, I feel that 端程山 is a sort of "sequel" song to 栞 [1], and this "yamahodo" expresses not just the sheer distance of the proverbial mountain range they still need to cover, but also the plentiful of experiences they have shared (=distance they have already travelled).

[1] mainly because of "ひとやすみしよう (Let's take a breather)" and "見つけた景色を たずさえながら ふりかえりながら (The views that we discovered While bringing them along, and looking back on them)" give the vibe of "let's put a bookmark in our story right now, take a break, and see how far we've come"

Consistent with this, some parts seem to allude to other MyGO songs. Not sure if this is simply just "In universe Tomori wrote the song" and props to the IRL lyricist for maintaining consistency of voice between songs, or if it is intentional due to the "looking back" aspect of "見つけた景色を たずさえながら ふりかえりながら"

栞 (as explained above) 人間になりたいうた ("looking down" and "shoe" motif from "don't realize the soles of my shoes...looking up a little more") 回層浮 ("Even if we went in circles", though the the original word in jpn (nor its parts) does not appear in 回層浮 so this might be a stretch) 焚音打 (continued use of "lighting a fire" motif in "焚いてる ", though maybe it's just coincidental) 春日影 ("ああ今なら　話せそうなんだ (Aah, if it's now, I think I can say them)", upgraded from "今ならば　分かる気がする (I think I understand now)" in Haruhikage from the CRYCHIC days)